Windows Server and Quad Core Processors

Question

A server with two Quads effectively has 8 proccessors but Windows server only supports 4. Which 4 will it use and how is this defined. Are the remaining completely idle.   Years ago I worked for NCR and while on a training course I was working on what was then a big server with 16 processors all being used but on Windows NT3.5 Server. This was because the special HAL it used teamed 4 processors together so the O/S only saw one.

DELL-Matthew P · Answer

The standard version of W2K3 R2 SP2 can use up to four quad core processors.  Microsoft's license is based on processor not the number of cores.   http://download.microsoft.com/download/6/8/9/68964284-864d-4a6d-aed9-f2c1f8f23e14/hyper_threading.doc

AlanKS · Answer

The document linked details the licensing requirements but does not explain how the O/S handle the individual cores. On my 2650 with 2 dual core processors both msinfo32 and the performance tab of the task manager show 4 processors, what would it do with 2 Quad core processors (if it supported them).   I recently rebuilt my test SBS server with a quad core and got a warning during installation that SBS only supports 2 processors, by the definition of the document I only had one. In my example from NCR the processors were on separate boards, 4 per board and the specially written HAL treated each board as a single processor. Does the standard HAL team 2 cores as one processor or do half of them become redundant?

Dev Mgr · Answer

The 2650 doesn't support dual core processors. You're seeing hyperthreaded processors.

SBS supports 2 processors. So if you were running quad core processors, SBS would support 2 quad cores, yielding 8 cores.

The HAL doesn't care if you're running 2 cores or 32 cores. The OS may limit how many processors (not cores!) the OS can see, but the HAL doesn't 'care'.

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Windows Server and Quad Core Processors

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